Lecture 20

Climate Change I: The Nature of the Challenge

Byeong-Hak Choe
bchoe@geneseo.edu

SUNY Geneseo

October 23, 2024

Climate Change I: The Nature of the Challenge

Introduction

Greenhouse Gases vs. Other Pollutants

  • Shared Attributes:
    • Like other pollutants, greenhouse gases (GHGs) contribute to environmental degradation and pose health risks.
    • Both types of pollutants require regulation and mitigation strategies to protect public health and ecosystems.
  • Unique Attributes of GHGs:
    • Global Scale: GHGs have a worldwide impact, unlike many pollutants which are confined to regional or local areas.
    • Irreversibility: Key GHGs, such as CO₂, have long atmospheric lifetimes, leading to persistent climate effects.
    • Uncertainty: There are significant uncertainties regarding the extent and timing of climate threats, complicating policy responses.

Introduction

Policy Design Implications

  • Global vs. National Solutions:
    • Addressing GHGs necessitates international cooperation, making policy design more complex compared to national pollutants.
  • Political Complexities:
    • International Cooperation Challenges:
      • Diverse national interests and economic dependencies on fossil fuels hinder unified action.
    • Climate-Intensified Scarcities:
      • Potential shortages of essential resources like water can exacerbate tensions between nations.
    • Climate Refugees:
      • Increased migration due to extreme weather events.

The Science of Climate Change: The Basics

Greenhouse Gases (GHGs)

  • Function of GHGs:
    • GHGs absorb long-wavelength (infrared) radiation emitted from the Earth’s surface and atmosphere.
    • This absorption traps heat, preventing it from escaping into space, thereby warming the planet.
  • Key Greenhouse Gases:
    • Carbon Dioxide (CO₂): Predominantly from fossil fuel combustion and industrial processes.
    • Methane (CH₄): Emitted during the production and transport of coal, oil, and natural gas, as well as from livestock and landfills.
    • Nitrous Oxide (N₂O): Released from agricultural activities, combustion of fossil fuels, and industrial processes.

The Science of Climate Change: The Basics

Current Concentrations

  • Historical Context:
    • In 2018, the World Meteorological Organization (WMO) reported that concentrations of CO₂, CH₄, and N₂O reached all-time highs.
  • Implications:
    • Elevated levels of these GHGs are directly linked to enhanced greenhouse effects, leading to global warming and climate change.

Major Greenhouse Gases

Carbon Dioxide (CO₂)

  • Sources:
    • Combustion of Fossil Fuels: Primary source from burning coal, natural gas, oil, and transportation fuels like gasoline.
    • Biomass Burning: Includes burning wood and other organic materials.
    • Industrial Processes: Chemical reactions in manufacturing products such as cement release significant CO₂.

Major Greenhouse Gases

Methane (CH₄)

  • Sources:
    • Fossil Fuel Production and Transport: Leakage during extraction and distribution.
    • Agricultural Practices: Enteric fermentation in livestock and rice paddies.
    • Waste Management: Decomposition of organic waste in landfills produces methane.

Major Greenhouse Gases

Nitrous Oxide (N₂O)

  • Sources:
    • Agriculture: Use of synthetic fertilizers and manure management.
    • Industrial Activities: Production of nitric acid and other chemicals.
    • Combustion Processes: Motor vehicle exhaust and biomass burning.

Human vs. Natural Factors

Natural Influences

  • Solar Energy Variations:
    • Changes in solar irradiance can affect Earth’s climate but are insufficient to explain recent warming trends.
  • Natural Climate Cycles:
    • Phenomena like El Niño and La Niña influence short-term weather patterns and regional temperatures.

Human vs. Natural Factors

Human Influence

  • Unambiguous Long-Term Warming:
    • Over the past century, the consistent increase in global temperatures cannot be solely attributed to natural factors.
  • IPCC Findings:
    • The Intergovernmental Panel on Climate Change (IPCC) Sixth Assessment Report (2021) states with high confidence that human activities are the primary drivers of recent climate change.

Global Warming Potential (GWP)

Definition and Importance

  • Global Warming Potential (GWP):
    • A metric that quantifies the amount of heat a greenhouse gas traps in the atmosphere over a specific time period, relative to CO₂.
  • Common Timeframe:
    • 100 years is the standard period for comparing GWP values.

Global Warming Potential (GWP)

GWP Values and Atmospheric Lifetimes

Gas GWP (100 years) Atmospheric Lifetime
CO₂ 1.0 Thousands of years
CH₄ 28–36 ~10 years
N₂O 265–298 >100 years
  • CO₂e Metric:
    • Carbon dioxide equivalent (CO₂e) aggregates the impact of multiple GHGs into a single value, facilitating comparison and policy-making.

Quantifying the Intensity of the Threats

Intergovernmental Panel on Climate Change (IPCC)

  • Establishment:
    • Formed in 1988 by the United Nations Environment Program (UNEP) and the World Meteorological Organization (WMO).
  • Membership:
    • Comprises 195 member countries.
  • Purpose:
    • Provide comprehensive scientific assessments on climate change, its implications, future risks, and strategies for adaptation and mitigation.

Quantifying the Intensity of the Threats

Key Findings from IPCC Sixth Assessment (2021)

  • Increased Intensity of Weather Events:
    • More intense rainfall leading to severe flooding.
    • Prolonged droughts in various regions.
  • Sea Level Rise:
    • Continued rise contributing to coastal flooding and erosion in low-lying areas.

Quantifying the Intensity of the Threats

Key Findings from IPCC Sixth Assessment (2021)

  • Cryosphere Changes:
    • Accelerated permafrost thawing, loss of seasonal snow cover, and melting of glaciers and ice sheets.
  • Ocean Ecosystem Impacts:
    • Disruptions to marine life and fisheries affecting human livelihoods.
  • Amplified Heat Waves:
    • More frequent and severe heatwaves affecting health and agriculture.

Quantifying the Intensity of the Threats

Additional Reports

  • State of the Climate 2020 (American Meteorological Society):
    • GHG Concentrations: Highest on record.
    • Temperature Records: 2020 was the third warmest year globally, the warmest without El Niño influence.
    • Sea Levels: Recorded the highest global sea levels.
    • Tropical Cyclones: Number of cyclones exceeded average levels.